Polymer beads incorporating magnetic particles are known. Such beads have been found to be particularly suitable for use in biomedical applications. In particular, the beads may be used for therapeutic or analytical purposes. For example, magnetic polymer beads may function as a carrier and permit the guiding and release of a drug at a specific site of a subject. The beads may also be used to provide hyperthermic treatment of tissue such as diseased tissue in a subject. Such polymer beads have also found application in immunoassays.
Numerous techniques have been developed over the years to produce polymer beads incorporating magnetic particles. These include layer-by-layer deposition techniques, classical heterogeneous polymerisation processes (e.g. emulsion, suspension, dispersion, microemulsion, and miniemulsion techniques), and the precipitation of magnetic materials within the pores of preformed polymer beads.
For most biomedical applications, it is generally important that the beads be produced with a uniform size and composition and with a relatively high magnetic particle content. Furthermore, it is also generally important that the magnetic particles be substantially uniformly dispersed throughout the polymer bead.
A considerable amount of research has been conducted to date on dispersion techniques for preparing polymer beads incorporating magnetic particles. Such techniques include the aforementioned classical heterogeneous polymerisation processes, which typically involve dispersing magnetic particles in a liquid phase and polymerising monomer to form polymer that encapsulates the particles.
Despite some success, the complexity of polymer particle nucleation in conventional dispersion polymerisation processes and the difficulties associated with controlling the stability of the dispersed magnetic particles have proven to be major obstacles in preparing the polymer beads efficiently and with high magnetic particle content. For example, the principle locus for particle nucleation in conventional emulsion polymerisation processes is generally either in the aqueous phase or in monomer-swollen micelles. However, the presence of magnetic particles dispersed in the aqueous phase can provide for additional nucleation sites at the surface of these particles. Accordingly, competition between these mechanisms can result in the formation of polymer beads with little or no magnetic particle content.
The effectiveness of dispersion techniques can also become problematic as the polymer beads are prepared with progressively small magnetic particles. In particular, as the magnetic particles become smaller (for example ≦100 nm) it becomes increasingly more difficult to maintain the particles in a dispersed state so as to produce beads having the particles substantially uniformly distributed therein (i.e. it becomes difficult to prevent aggregation of the magnetic particles during bead manufacture).
An opportunity therefore remains to address or ameliorate one or more disadvantages or shortcomings associated with existing polymer beads incorporating magnetic particles and/or their methods of manufacture, or to at least provide a useful alternative to conventional polymer beads incorporating magnetic particles and/or their methods of manufacture.